A self-locking fastener, particularly a nut or a bolt of the above-said type, is known from Dutch patent application No. 70 13558. With said known fastener the bearing surface of the nut or the bolt head is formed at the lower side of a flange, which over the whole periphery extends outside the hexagonal outer surface of the nut or the bolt head. Said bearing surface is provided with an annular row of radial teeth, surrounded at the outer ends by an edge portion of the flange which is not provided with teeth. With said known fastener the crests of the radial teeth are located flush with the smooth edge portion of the flange or with the highest point thereof at the lower side respectively and the height of the teeth increases in radial direction from the axis of the fastener toward the periphery of the flange. With said known toothing of the bearing surface, the spacing of the teeth and therewith the depth of the teeth increases in a direction from the inner diameter of the flange toward the outer diameter of the flange. The crests of the teeth are perpendicular to the axis of the article and are flush therewith in a flat plane. The roots of the teeth enclose an angle with the axis of the fastener and are as it were located on a cone surface. With the known fastener the bearing surface only consists of a narrow ring in the vicinity of the outer periphery of the flange, the shape of which can vary between a flat surface and a cone.
The known fastener possesses relatively long teeth, so that in the friction between the flange and the underlying material a relatively high variation occurs.
The teeth of the known fastener comprise a relatively great maximal height and moreover the bearing surface of the known fastener is relatively small and only in some cases flat. With the known fastener when detaching the same, a relatively small surface is described by a tooth with the same angle of rotation, by which relatively little underlying material is deformed.
As a result of the above characteristics of the known fastener, particularly of its toothing at the bearing surface, said known fastener looses a relatively great deal of its resistance to rotation in the opposite direction during setting.
During the formation of the teeth on the bearing surface of the known fastener by means of a stamp it is necessary, to form the teeth completely in the vicinity of the outer edge of the flange, that the teeth are extra strongly pressed at the inner edge of the flange. Therefore a much higher stamping pressure is needed at the inner edge of the flange than in the vicinity of the outer edge of the flange. With the production of the known fastener the useful life of the stamp will be relatively short for that reason.
The object of the present invention is to remove said objections against the known fastener and the stamp respectively for making said fastener.